“Traprock Quarry” In the early 20th Century, a small quarry produced crushed diabase basalt for use in roadways. Remnants of the crushing building stand southwest of the Flat Rock Brook Building.
The diabase basalt forming the Palisades Cliffs and similar rocks were called “traprock” (or “trapp rock” or similar terms, meaning “stepped rock”) by Dutch settlers. Large chunks were broken into small pieces for various uses (Fig. 1). By the late 19th century, several large-scale quarries operated along the Hudson River. One of the most notorious was the Carpenter Brothers quarry, just north of where the George Washington Bridge was later constructed (Figs. 2). The noise and damage to the scenic cliffs alarmed many members of the New Jersey and New York Women’s Clubs. They banded together and induced the State Legislatures to create the Palisades Interstate Park in the early 20th century. This ended quarrying along the cliffs. But to meet the need for crushed stones for highway and railroads, a small quarry was opened in Englewood on the western slope of the Palisades. It operated for several years into the 1920s. As in most quarries, drills created holes into which dynamite or other explosive materials were placed. The diabase was blasted into large pieces which were then crushed into smaller sizes before being trucked away to serve as the base material beneath roadways. Remnants of the crushing building (Fig. 3) still exist southwest of the Flat Rock Brook Nature Center interpretive building. Beginning in the 1970s, the quarry became the centerpiece for the Flat Rock Brook Nature Center, now a 150-acre preserve.
Fig. 1. Crushed diabase basalt (credit: https://geology.com/articles/trap-rock/ )
Fig. 2 Images of the Carpenter Brothers Quarry along the Palisades, c. 1897. http://nycedges.blogspot.com/2011/11/ Fig. 3. Remnants of the Flat Rock Brook quarry crushing building (below)
Fig. 4 The Quarry in the Flat Rock Brook Nature Center
Drill holes in slab of diabase basalt, Flat Rock Brook quarry
More information
Dustin Griffin “The History of Flat Rock Brook”
Wikipedia “Trap rock”
Geology.com “Trap rock”
Tilcon New York “Traprock Quarries”